1. Field
Disclosed herein is a method and an apparatus for casting concrete beams or concrete elements including one or more hollow cores by slipforming.
2. Description of Related Art
Slipforming is a method generally used for casting concrete elements. Casting of beams can be performed by using between walls between the products to be cast, and casting of hollow-core elements including hollow cores can be performed by using hollow-core tubes. The casting is typically performed in two steps. The mass forming the lower portion of the hollow-core slabs is fed in the first step onto the casting bed before the hollow-core tubes are put in place. When the hollow-core tubes are in their places, the mass to form the upper portion of the slab is fed onto the tubes and between them. A traditional way is to cast by slipforming a long uniform cast piece, which after hardening is sawn into parts with desired length. Respectively, the casting of beams is performed in two steps. The mass of concrete mixture is first fed to form the lower portion of the beam, and when the feeding point of the mass for the upper part reaches its location, the mass to form the upper part of the beam will be fed.
In slipforming, the heights of the products to be cast are determined according to the loads to be exerted to the products. The portion of the hollow cores of the volume of the slab is as large as possible, taking into account the strength requirements for the slab, in order to produce a slab as light as possible and to minimize the amount of the raw material. The amount and number of hollow cores in the slab varies usually so, that in a low slab there is a plurality of smaller cores and along with increasing the height of the slab of the same width, the number of the hollow cores is decreased and their diameter is increased.
One and the same slipforming apparatus is usually used for products with different heights. When the size of the product to be cast is changed, typically the whole hollow-core tube series, in other words the mandrel series, of the slipforming apparatus is changed into a tube series corresponding the amount and/or size of the hollow cores of the other product to be cast. At the same time the mass compacting members are changed, as well to correspond to the amount and/or size of the mandrels. Correspondingly, also the side walls for forming the edges of the slab have to be changed in accordance with the requirements for the new height of the product to be cast, for example in order to change the location or shape of the longitudinal groove to be formed to the upper edge of the slab. Changing work is quite time-consuming and after the change, the slipforming apparatus has to be readjusted for the new product height. As the height of the products to be cast can vary quite a lot and the lots to be produced can be relatively small, the settings of the apparatus, especially the hollow-core forming members, must be simply and quickly changeable for different products.